The issue is related to an out-of-bounds read when setting HMAC data in the SRv6 layer of the Linux kernel. This configuration is realized via netlink through four attributes: `SEG6 ATTR HMACKEYID`, `SEG6 ATTR SECRET`, `SEG6 ATTR SECRETLEN`, and `SEG6 ATTR ALGID`. Because the `SECRETLEN` attribute is decoupled from the actual length of the `SECRET` attribute, it is possible to provide invalid combinations, allowing an out-of-bounds read of up to 64 bytes to occur past the `skb` end pointer and into `skb shared info`. This can be exploited by providing a crafted netlink message. The estimated number of potentially affected devices worldwide is not specified. There is no information about real-world incidents where this issue was exploited.